Thin film transistor substrate and display

ABSTRACT

The invention provides a thin film transistor substrate includes: a substrate; and a plurality of transistors, wherein each of the transistors includes a gate electrode disposed on the substrate; a first diffusion barrier layer disposed on the substrate and covering an upper surface and a ring sidewall of the gate electrode; a gate insulating layer disposed on the first diffusion barrier layer; an active layer disposed on the gate insulating layer and over the gate electrode; a source electrode disposed on the substrate and electrically connected to the active layer; a drain electrode disposed on the substrate and electrically connected to the active layer; and a protective layer covering the source electrode and the drain electrode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/560,570, filed on Dec. 4, 2014, issued as U.S. Pat. No. 9,281,350,and entitled “Thin film transistor substrate and display”, which claimspriority of U.S. patent application Ser. No. 13/910,424, filed on Jun.5, 2013, issued as U.S. Pat. No. 8,933,442, the entirety of which isincorporated by reference herein. The U.S. patent application Ser. No.13/910,424, issued as U.S. Pat. No. 8,933,442, claims priority of TaiwanPatent Application No. 101120063, filed on Jun. 5, 2012, the entirety ofwhich is also incorporated by reference herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a thin film transistor, and inparticular relates to a thin film transistor substrate, having adiffusion barrier layer, and a display using the same.

Description of the Related Art

With the progress in display technologies, lifestyles of humans havebecome more convenient with the assistance of display devices. Withdemands of being light and thin, the flat panel displays (FPD) have nowbecome most popular displays. Among the variety of FPDs, liquid crystaldisplays (LCDs) are highly preferred due to advantages such as,providing the ability for more efficient space utilization, low powerconsumption, no radiation output, and low electromagnetic interference(EMI).

Liquid crystal displays are mainly composed of an active arraysubstrate, a color filter substrate, and a liquid crystal layer locatedtherebetween. The active array substrate has an active region and aperiphery circuit region. The active arrays are located in the activeregion, and the driving circuits having a plurality of thin filmtransistors are located in the periphery circuit region. In thin filmtransistors, a gate insulating layer is used to separate a gateelectrode from an active layer to insulate the gate electrode from theactive layer. However, it is easy for the material of the gate electrodeto diffuse into the gate insulating layer, which affects the insulatingproperty of the gate insulating layer.

BRIEF SUMMARY OF THE INVENTION

An embodiment of the invention provides a thin film transistor substratewhich includes: a substrate; and a plurality of thin film transistorsdisposed on the substrate, wherein each of the thin film transistorscomprises: a gate electrode disposed on the substrate; a first diffusionbarrier layer disposed on the substrate and covering the gate electrode;a gate insulating layer disposed on the first diffusion barrier layer;an active layer disposed on the gate insulating layer and over the gateelectrode; a source electrode disposed on the substrate and electricallyconnected to the active layer; a drain electrode disposed on thesubstrate and electrically connected to the active layer; and aprotective layer covering the source electrode and the drain electrode.

An embodiment of the invention provides a display, which includes: athin film transistor substrate; a substrate disposed opposite to thethin film transistor substrate; and a display medium disposed betweenthe thin film transistor substrate and the substrate.

A detailed description is given in the following embodiments withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thesubsequent detailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a thin film transistor substrateaccording to an embodiment of the present invention;

FIGS. 2 and 3 are cross-sectional views of thin film transistorsubstrates according to embodiments of the present invention;

FIG. 4 is a cross-sectional view of a thin film transistor substrateaccording to an embodiment of the present invention;

FIGS. 5 and 6 are cross-sectional views of thin film transistorsubstrates according to embodiments of the present invention; and

FIG. 7 is a cross-sectional view of a display according to an embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

It is understood, that the following disclosure provides many differentembodiments, or examples, for implementing different features of theinvention. Specific examples of components and arrangements aredescribed below to simplify the present disclosure. These are, ofcourse, merely examples and are not intended to be limiting. Inaddition, the present disclosure may repeat reference numbers and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.Furthermore, descriptions of a first layer “on,” “overlying,” (and likedescriptions) a second layer, include embodiments where the first andsecond layers are in direct contact and those where one or more layersare interposing the first and second layers.

FIG. 1 is a cross-sectional view of a thin film transistor substrateaccording to an embodiment of the present invention. Referring to FIG.1, in the present embodiment, the thin film transistor substrate 100includes a substrate 110 and a plurality of thin film transistors S onthe substrate 110. It should be noted that, for the sake of simplicity,FIG. 1 shows only one thin film transistors S for illustration, but doesnot limit the invention thereto.

Each thin film transistor S includes a gate electrode 120, a firstdiffusion barrier layer 130, a gate insulating layer 140, an activelayer 150, a source electrode 160, a drain electrode 170, and aprotective layer P. Furthermore, the thin film transistor substrate 100may optionally include an insulating layer 180.

Specifically, the gate electrode 120 is disposed on the substrate 110.The substrate 110 includes, for example, glass or other suitabletransparent materials. The gate electrode 120 includes, for example,copper, aluminum, molybdenum, or other suitable conductive materials.

The first diffusion barrier layer 130 is disposed on the substrate 110and covers an upper surface 122 and a surrounding sidewall 124connecting to the upper surface 122 of the gate electrode 120.Specifically, in the present embodiment, the first diffusion barrierlayer 130 conformally covers the upper surface 122 and the surroundingsidewall 124 of the gate electrode 120.

The first diffusion barrier layer 130 includes, for example, nitrides,metal oxides, combinations thereof, or other materials suitable toprevent the materials of the gate electrode 120, such as copper, fromdiffusing into the gate insulating layer 140. Specifically, the firstdiffusion barrier layer 130 may include silicon nitride, aluminum oxide,titanium oxide, hafnium oxide, silicon aluminum oxide, or combinationsthereof. Furthermore, a thickness T1 of the first diffusion barrierlayer 130 is, for example, about 10 Å to about 5000 Å. In oneembodiment, the thickness T1 of the first diffusion barrier layer 130may be about 500 Å to about 1000 Å.

The gate insulating layer 140 is disposed on the first diffusion barrierlayer 130. The gate insulating layer 140 includes, for example, siliconoxide, silcon nitride or other suitable insulating materials. Thestruction of the gate insulating layer 140 is single layer ormulti-layer. The active layer 150 is disposed on the gate insulatinglayer 140 and over the gate electrode 120, wherein the upper surface 122of the gate electrode 120 faces the active layer 150. The active layer150 includes, for example, indium gallium zinc oxide (IGZO) or othersemiconductor materials suitable for the active layer.

The insulating layer 180 is disposed on the active layer 150 and coversthe gate insulating layer 140, wherein the source electrode 160 and thedrain electrode 170 are disposed on the insulating layer 180 and passesthrough the insulating layer 180 to connect to the active layer 150. Thesource electrode 160 and the drain electrode 170 include, for example,copper, aluminum, molybdenum, or other suitable conductive materials.

The thin film transistor substrate 100 may optionally further include aprotective layer P, wherein the protective layer P is disposed on thesource electrode 160 and the drain electrode 170 and covers theinsulating layer 180 to protect the source electrode 160, the drainelectrode 170 and the insulating layer 180 from environmentalcontaminants. The protective layer P includes silicon oxide or othersuitable insulating materials.

Furthermore, the thin film transistor substrate 100 may optionallyinclude a first bottom layer B1 and a second bottom layer B2.Specifically, the first bottom layer B1 is formed between the substrate110 and the gate electrode 120 to bond the substrate 110 to the gateelectrode 120. The second bottom layer B2 is formed between the sourceelectrode 160 (or the drain electrode 170) and the active layer 150 toreduce the contact resistance between the source electrode 160 (or thedrain electrode 170) and the active layer 150. The first bottom layer B1and the second bottom layer B2 may include molybdenum, titanium,aluminum, chromium, alloys thereof, copper-manganese alloy, orcombinations thereof. The first bottom layer B1 and the second bottomlayer B2 have thicknesses ranging from about 1 Å to 3000 Å.

It should be noted that, in the present embodiment, the first diffusionbarrier layer 130 completely covering the gate electrode 120 mayeffectively prevent the materials of the gate electrode 120 fromdiffusing into the gate insulating layer 140 to improve the electricalstability of the thin film transistor substrate 110.

FIGS. 2 and 3 are cross-sectional views of thin film transistorsubstrates according to embodiments of the present invention. Referringto FIG. 2, the thin film transistor substrate 200 of the presentembodiment is structurally similar to the thin film transistor substrate100 of FIG. 1, except that the thin film transistor S of the thin filmtransistor substrate 200 of the present embodiment further includes athird diffusion barrier layer (i.e. a cap layer) 210.

Specifically, the third diffusion barrier layer 210 covers the uppersurface 122 of the gate electrode 120 and is located between the gateelectrode 120 and the first diffusion barrier layer 130 to prevent thematerials of the gate electrode 120 from diffusing into the gateinsulating layer 140. The thickness T2 of the third diffusion barrierlayer 210 ranges about 1 Å to about 3000 Å. The third diffusion barrierlayer 210 includes, for example, molybdenum, titanium, aluminum,chromium, alloys thereof, or other materials suitable to prevent thematerials of the gate electrode 120 (e.g. copper) from diffusing intothe gate insulating layer 140. In the present embodiment, an edge 212 ofthe third diffusion barrier layer 210 is aligned with an edge 126 (thesurrounding sidewall 124) of the gate electrode 120. In anotherembodiment, as shown in FIG. 3, the edge 212 of the third diffusionbarrier layer 210 is recessed from or aligned with the edge of the gateelectrode 120. In the present embodiment, the edge of the thirddiffusion barrier layer 210 is recessed from the edge of the gateelectrode 120. That is to say, the edge 212 of the third diffusionbarrier layer 210 shrinks relative to the edge 126 of the gate electrode120.

It should be noted that, because the edge 212 of the third diffusionbarrier layer 210 is aligned with the edge 126 of the gate electrode 120(as shown in FIG. 2) or is recessed from the edge 126 of the gateelectrode 120 (as shown in FIG. 3), the first diffusion barrier layer130 covering the third diffusion barrier layer 210 may cover thesurrounding sidewall of the gate electrode 120 well.

FIG. 4 is a cross-sectional view of a thin film transistor substrateaccording to an embodiment of the present invention. Referring to FIG.4, the thin film transistor substrate 400 of the present embodiment isstructurally similar to the thin film transistor substrate 100 of FIG.1, except that the gate insulating layer 140 of the thin film transistorsubstrate 400 of the present embodiment includes a first film 142 and asecond film 144. Specifically, the first film 142 covers the firstdiffusion barrier layer 130, and the second film 144 is located on thefirst film 142. The hydrogen content of the second film 144 is less thanthat of the first film 142, and the hydrogen content of the second film144 is less than or equal to about 20 atomic % and more than 0 atomic %.

The manufacturing method of the first film 142 and the second film 144of an embodiment is described as follows. Firstly, a high hydrogencontent process with a high deposition rate is performed to deposit thefirst film 142 onto the first diffusion barrier layer 130, wherein theratio of nitrogen oxide to silane is, for example, less than 60 in thehigh hydrogen content process, and the deposition rate is, for example,1000 Å per minute (in thickness). Then, a low hydrogen content processwith a low deposition rate is performed to deposit the second film 144onto the first film 142, wherein the ratio of nitrogen oxide to silaneis, for example, larger than 60 for the low hydrogen content process,and the deposition rate is, for example, 500 Å per minute (inthickness).

Because hydrogen atoms may affect the electrical property of the activelayer 150 and the gate insulating layer 140 needs to be thick enough, inthe present embodiment, the first film 142 with the high hydrogencontent and the high deposition rate is firstly deposited on the firstdiffusion barrier layer 130, and then the second film 144 with the lowhydrogen content and the low deposition rate is deposited on the firstfilm 142. As such, the first film 142 with the high deposition rateprovides enough film thickness, and the active layer 150 only contactsthe second film 144 with the low hydrogen content (not the first film142 with the high hydrogen content) to prevent the hydrogen atoms fromaffecting the electrical property of the active layer 150. The thicknessT3 of the second film 144 ranges, for example, from about 500 Å to about1000 Å. The total thickness T4 of the gate insulating layer 140 is, forexample, 5000 Å.

FIGS. 5 and 6 are cross-sectional views of thin film transistorsubstrates according to embodiments of the present invention. Referringto FIG. 5, the thin film transistor substrate 500 of the presentembodiment is structurally similar to the thin film transistor substrate100 of FIG. 1, except that the thin film transistor S of the thin filmtransistor substrate 500 of the present embodiment further includes asecond diffusion barrier layer (i.e. a cap layer) 190.

Specifically, the second diffusion barrier layer 190 is disposed on thesource electrode 160 and the drain electrode 170 and covers theinsulating layer 180. The second diffusion barrier layer 190 mayinclude, for example, silicon nitride, aluminum oxide, titanium oxide,hafnium oxide, silicon aluminum oxide, or combinations thereof. Thematerial of the second diffusion barrier layer 190 may be, for example,the same as that of the first diffusion barrier layer 130. The materialof the second diffusion barrier layer 190 may be, for example, differentfrom that of the protective layer P. The thickness T5 of the seconddiffusion barrier layer 190 ranges, for example, from about 1000 Å to2000 Å. In the present embodiment, the second diffusion barrier layer190 is located between the insulating layer 180 and the protective layerP.

In other embodiments, as shown in FIG. 6, the second diffusion barrierlayer 190 may completely replace the protective layer P, so in the thinfilm transistor substrate 600, the second diffusion barrier layer 190may be used to cover and protect the source electrode 160, the drainelectrode 170, and the insulating layer 180.

FIG. 7 is a cross-sectional view of a display according to an embodimentof the present invention. Referring to FIG. 7, the display 700 of thepresent embodiment includes a thin film transistor substrate 710, asubstrate 720, and a display medium 730 disposed therebetween. The thinfilm transistor substrate 710 may be the thin film transistor substrateas shown in FIGS. 1-6, and the display medium 730 is a liquid crystallayer or an organic light emitting layer. The substrate 720 is, forexample, a color filter substrate or a transparent substrate.

In view of the foregoing, in the present invention, a diffusion barrierlayer completely covering the gate electrode is formed between the gateelectrode and the gate insulating layer to prevent the materials of thegate electrode from diffusing into the gate insulating layer to improvethe electrical stability of the thin film transistor substrate.

While the invention has been described by way of example and in terms ofthe preferred embodiments, it is to be understood that the invention isnot limited to the disclosed embodiments. To the contrary, it isintended to cover various modifications and similar arrangements (aswould be apparent to those skilled in the art). Therefore, the scope ofthe appended claims should be accorded the broadest interpretation so asto encompass all such modifications and similar arrangements.

What is claimed is:
 1. A thin film transistor substrate, comprising: asubstrate; and a plurality of thin film transistors disposed on thesubstrate, wherein each of the thin film transistors comprises: a gateelectrode disposed on the substrate; a first layer disposed on the gateelectrode and comprising silicon nitride; a second layer disposed on thefirst layer and comprising silicon oxide, wherein a hydrogen content ofthe first layer is greater than a hydrogen content of the second layer;a metal oxide layer disposed on the second layer and over the gateelectrode; a source electrode disposed on the substrate and electricallyconnected to the metal oxide layer; a drain electrode disposed on thesubstrate and electrically connected to the metal oxide layer; and aprotective layer covering the source electrode and the drain electrode.2. The thin film transistor substrate as claimed in claim 1, wherein themetal oxide layer comprises indium gallium zinc oxide.
 3. The thin filmtransistor substrate as claimed in claim 1, wherein each of the thinfilm transistors further comprises a bottom layer formed between thesubstrate and the gate electrode.
 4. The thin film transistor substrateas claimed in claim 1, wherein each of the thin film transistors furthercomprises a bottom layer formed between the source electrode and themetal oxide layer, and between the drain electrode and the metal oxidelayer.
 5. The thin film transistor substrate as claimed in claim 1,wherein a thickness of the first layer is greater than a thickness ofthe second layer.
 6. The thin film transistor substrate as claimed inclaim 5, wherein the thickness of the second layer is about 500angstroms to 1000 angstroms.
 7. A display, comprising: a thin filmtransistor substrate; a substrate disposed opposite to the thin filmtransistor substrate; and a display medium disposed between the thinfilm transistor substrate and the substrate; wherein the thin filmtransistor substrate comprises: a substrate; and a plurality of thinfilm transistors disposed on the substrate, wherein each of the thinfilm transistors comprises: a gate electrode disposed on the substrate;a first layer disposed on the gate electrode and comprising siliconnitride; a second layer disposed on the first layer and comprisingsilicon oxide, wherein a hydrogen content of the first layer is greaterthan a hydrogen content of the second layer; a metal oxide layerdisposed on the second layer and over the gate electrode; a sourceelectrode disposed on the substrate and electrically connected to themetal oxide layer; a drain electrode disposed on the substrate andelectrically connected to the metal oxide layer; and a protective layercovering the source electrode and the drain electrode.
 8. The display asclaimed in claim 7, wherein the display medium is a liquid crystallayer.
 9. The display as claimed in claim 7, wherein the display mediumis an organic light emitting layer.